<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
  </head>

  <body>
    <div id="app">
      <h2>{{counter}}</h2>
      <!-- <button v-on:click="counter++">+</button>
    <button v-on:click="counter--">-</button> -->
      <!-- <button v-on:click="increment">+</button>
    <button v-on:click="decrement">-</button> -->
      <button @click="increment">+</button>
      <button @click="decrement">-</button>
    </div>

    <script src="../js/vue.js"></script>
    <script>
      const app = new Vue({
        el: '#app',
        data: {
          counter: 0
        },
        methods: {
          increment() {
            this.counter++
          },
          decrement() {
            this.counter--
          }
        }
      })
    </script>
  </body>
</html>
